This application is based on and claims the benefit of German Patent Application No. 10203900.3 filed Jan. 31, 2003, which is incorporated by reference herein.
The invention relates to an electrical line having at least one electrical conductor enclosed by temperature-resistant insulation which ensures the functionality of the line in case of fire (European Patent 0 106 708 B1).
Such lines or cables are used as power lines or as information or data transmission lines, for example. The conductors of same (at least one conductor) are insulated with a specialized material which in case of fire ensures the functionality of a corresponding line for a specified time period. The power supply to machines, apparatus, and equipment is maintained during this time period, and information can be transmitted during this time as well. The time period should be long enough so that, for example, all persons present in a building can be notified and the lighting in the building remains on until the persons have left the building, and materials have been moved to a safe place, if necessary. The time period which can be preset by the user is from 30 minutes to 3 hours, for example.
In the known line according to aforementioned European Patent 0 106 708 B1, an insulation material is used which comprises a mica band, a layer made of polytetrafluoroethylene (PTFE), and a glass fabric coated with PTFE. The PTFE can resist temperatures of up to approximately 600xc2x0 C. At higher temperatures
the PTFE disintegrates into ash. A line insulated in this manner has a high fire load, which in many cases is unacceptable. In a fire, the line produces toxic and chemically corrosive gases (smoke) on account of the fluorine, which can attack and destroy metals and electrical or electronic circuits.
The object of the invention is to improve the aforementioned line so that its functionality is ensured with a greatly reduced fire load and without the danger of consequential damage.
This object is achieved by the invention by the fact that
the insulation comprises at least one multifilament thread made of glass which is wound around the conductor and whose windings are contiguous so as to create a completely closed sleeve for the conductor, and
a thin protective layer of a halogen-free, temperature-resistant insulation material is applied all over the sleeve.
Since the protective layer which serves primarily as a mechanical support for the windings of the multifilament thread can be designed using a small amount of material, the fire load of this line is reduced to essentially zero. In addition, the material of the protective layer is free of halogen-containing substances, so that in case of fire no gases can be produced which are harmful to the environment. The protective layer can also be used to apply identification marks on the particular line. The insulated line is very simple to design and manufacture, and is easily assembled due to the fact that the multifilament thread can be removed in any desired length from the conductor simply by pulling in the axial direction. Because of the basically adequate sleeve made of multifilament thread as a single layer of insulation, the line has small dimensions, so that the material used for additional layers can be reduced when the line is combined with at least one additional line in a cable.